Tear resisting rubber sheeting



A ril 23, 1940. A. N. IKNAYAN TEAR RESISTING RUBBER SHEETING Filed Oct.8, 1957 INVENTOR ALFRED N. IKNAYAN BY k- ATTORNEYS.

Patented Apr. 23, 1940 UNITED s'r'rss I TEAR RESISTHNG RUBBER SHEE'EING'New Jersey Application October 8, 1937, Serial No. 167,938

12 Claims. (iii. 152-349) This invention relates to tear resistingrubber articles, and in particular it relates to inner tubes havingwalls of rubber characterized by the feature of limiting the length oftears that might occur in the inner tube wall.

In general, the invention comprises an arrangement of separationsextending partly through the wall of a rubber article, whereby tearswhich reach the separations are hindered from proceeding further in viewof the difliculty of originating tears at the marginal wall of theseparation.

When a tear or cut is initiated in a sheet of vulcanized rubber there isa tendency for the' tear to increase rapidly with but very little strainin the rubber. It is considerably more dificult to start a tear at theedge of a sheet of vulcanized rubber than it is to increase the lengthof the tear after it is started. By utilizing this characteristic, Ibreak up the continuity of the sheet of rubber through the incorporationtherein of separations which, in efiect, function as marginal edges andas such resist continuation of atear.

In the mounting inner tubes and tire casings in assembly with a tirerim, particularly a rim of the drop center type, it frequently occursthat the inner tube is partially inflated before the tire is in fullengagement with the bead seats of the rim. As a result of thiscondition, the tube becomes stretched excessively at localized portions,which stretched condition is not entirely relieved upon completion ofthe mounting of the assembly. Thereafter, when the tube is in operationfailure is likely to occur in such excessively stretched zones. Completefailure of the tube may be originated by the pinching between the tirebead and the rim, by blow-outs, or by chafing conditions resulting fromirregularities in the. tire fabric.

In such inner tube failures a small tear or puncture occurs in the wallof the tube, and due to the force of the compressed air passing out ofthe tube and the tendency of the tube to tear easily after the tearoriginates, the resultant condition of the tube is such that the tear istoo long to permit of satisfactory repair. 1

It is, therefore, among the objects .of the invention to provide a sheetof rubber having characteristics which will function to minimize thetearing of the sheet, and to provide an inner tube capable of beingsatisfactorily repaired in the usual manner after failure. I

- These and other objects and advantages will appear more fully in thefollowing detailed description .of a preferred embodiment of theinvention and with reference to the drawing in which:

Fig. 1 is a perspective view of a sheet of rubber embodying the featuresofv the invention;

Fig. 2 is a perspective view, partly broken away, of the sheet in theprocess of manufacture;

Fig. 3 is a perspective view, in section, of an inner tube showingfeatures of the invention embodied therein; and,

Fig. 4 is a perspective view, in section, of an inner tube, illustratinga modification of the inner tube shown in Fig. 3.

Referring to the drawing, and in particular to Fig. 1, I show anembodiment of the invention in the form of a sheet of rubber l having aplurality of separations Z in the form of circular paths, the axes ofwhich extend substantially in a'transverse manner relative to the-planeof the sheet of rubber l. the circular paths extend in depth to aboutone half of the thickness of the sheet of rubber 0. Effective resultsmay be obtained by having the separations extend to a depth of at leastone The separations 2 forming fourth of the thickness of the sheet, andnot in excess of three fourths of the sheet thickness. The number andarrangement of the circular paths are such that a tear originating inany part of the strip and running in substantially a straight lineshould engage with one of the separations, resulting in greaterresistance of the sheet of rubber against continuation of thetear. Ihave found that, by staggering the various" rows of circular paths, atear when initiated will communicate with one of the separations beforethe tear becomes comparatively long;

In order that the fabrication, construction and function of the tearresisting material may be understood, reference may be made to Fig. 2

which illustrates a strip of the material in process of manufacture;

The strip l comprises a base layer 3 and a perforated layer 4'. Bothlayers are of unvulcanized rubber, and may be of the same materialcomposition, although efiective results may be obtained by formingtheperforated layer 4 of a. rubber stock having tougher-characteristics.This will increase the tear resisting quality of the sheet.

The perforated layer 4 is provided with a, plu- '60 rality of holes orperforations 5 extending through the layer of rubber. These perforations5 are'formed in the layer 4 prior to the application of the layer 4 to-the base layer 3. Any suitable means; such .as a punching operation,

may be employed to make the perforations in the layer 4. The perforatedlayer 4 is placed in laminated relation with the base layer 3 while thelayers are in their unvulcanized state. Under this condition, the layer4 will adhere readily to the layer 3. If desired, the layers may berolled together to insure proper adhesion.

After the layers 3 and 4 are properly adhered together, the laminatedsheet thus formed is subjected to lubrication. A practical means ofaccomplishing this result is to subject the laminated sheet to a dustingoperation with a medium such as powdered soapstone or mica. In thedusting operation the walls of the perforations 5 are well coated withthe dusting medium.

In the next operation the strip I formed of the laminated layers 3 and 4is vulcanized under heat and pressure. 4 is placed adjacent the moldsurface and pressure exerted against the exposed surface of the baselayer 3. While this is the preferred method of placing the strip in thevulcanizing mold, it is obvious that various combinations of directingpressure and positioning the strip within the mold will operate toaccomplish results which are substantially .satisfactory.

Due to the application of the lubricating material, such as soapstone,the rubber of the base layer 3 will not merge with the walls of theperforations 5. However, an adherence or slight vulcanization betweenthe different rubber layers may take place at the walls of theperforations. Upon vulcanization, the principal adjoining surfaces ofthe layers 3 and 4 merge together to form a unitary sheet of rubber. Asshown in Fig. l, a sheet of rubber is formed having a plurality ofcircular paths defining lines of demarcation between the differentlayers of rubber composition. When the rubber sheet is under extensionany union between the rubber compositions at the walls of theperforations becomes broken, with the result that the circular pathsdefine separations. Any union that may exist between the rubbercompositions at the circular paths is broken with much less strain inthe rubber than that required to produce a tear in rubber.

When the under side or exposed surface of the base layer 3 is subjectedto fluid pressure, as distinguished from confinement in a mold, a.plurality of indentations 6 are formed in complementary relation withthe perforations. This is due to the flowing of rubber stock from thebase layer 3 intothe perforations 5 in the layer 4.

In Fig. 3 a practical embodiment of the tear resisting rubber is shownin the form of an inner tube 1. In this embodiment the tear resistingfeature of the rubber is applied to the rim side of the inner tube, andincludes that region extending over one half of the tube when measuredtransversely.

The tear resisting layer may be applied to the tread side only of theinner tube or it may be applied to the entire surface of the inner tube,

- such as shown by-the inner tube 8 in Fig. 4.

In manufacturing inner tubes having a tear resisting layer of rubber,the embodiment may be manufactured by extruding the inner tube in theusual manner and thereafter applying a perforated layer to the outersurface of the tube. After this operation, the conventional practice ofmanufacturinginner tubes may be followed; that is, the tubes arespliced, dusted with soapstone, and vulcanized in conventional innertube molds.

The laminated'layers 3 and 4 as shown in Fig. 2 are representative ofthe tear resisting formation Preferably, the perforated layer of theinner tubes. As thus applicable to finished inner tubes, I find thepreferred thickness of the base layer 3 to be in the order of .055 inch,and the preferred thickness of the perforated layer 4 to be .040 inch.After vulcanization, and due to the fiow of rubber from the base layer 3into the perforations, the approximate thickness of the laminated sheetis in the order of .075 inch.

Good results in restricting the tearing of inner tubes may be obtainedby providing at least eight perforations per square inch. It isdesirable, however, to increase the number of perforations to abouteighteen perforations per square inch. This may be accomplished byproviding holes of a diameter of three sixteenths of an inch spaced onefourth of an inch on centers. The holes or perforations should bearranged so that it will be difficult to run a substantially straightline on the perforated sheet without coming into contact with at leastone of the perforations in a relatively short distance.

It is preferable that the separations in the finished shete describe acircular path, or at least a closed curved path. By staggering thearrangement of such separations, and placing them relatively closetogether, an initial tear will lengthen only a short distance before itreaches a separation. The tear then tends to proceed along the path ofthe separation. Because the separation is short and describes a closedpath, the tear is restricted in its progress to the area defined by theclosed path. In order to proceed farther, it would be necessary to starta new tear in the outer perforated layer. A curved path for theseparation is less conducive to tearing than an angular path which has adiscontinuous break in its length.

The relatively short length of a tear which occurs in this materialpermits the application of a relatively small patch to repair it. Theouter surface of the material is smooth enough to accommodate avulcanized patch or a patch secured by self-curing cement, witheffective results.

My invention contemplates within its scope the principle of providing avulcanized rubber material havinga plurality of separations of readilyseparable unions forming marginal walls which operate to minimizetearing of the rubber sheet.

While I have shown and described certain present preferred embodimentsof my invention, it is to be understood that it may be otherwiseembodied within the spirit thereof and the scope of the appended claims.

Having thus described my invention, what I claim and desire to protectby Letters Patent is: 1. A tear resisting article comprising a wallformed of laminations of different rubber compositions united throughouttheir faces, said wall having a plurality of crevices extending from anouter surface to said united faces, said crevices defining closed paths,each of said paths being separate from the others.

2. An inner tube having a wall comprising inner and outer laminae ofrubber composition, said outer lamina having perforations extendingtherethrough, said inner lamina being vulcanized to the inner face ofthe outer lamina and having portions extending into said perforations todefine walls opposing the lateral walls of said perforations.

3. An inner tube having a wall comprising inner and outer laminae ofrubber composition, said outer lamina having perforations extendingtherethrough, said inner lamina being substantially continuously securedto the inner face of the outer lamina and having portions extending intosaid perforations to define walls opposing the lateral walls of saidperforations.

4. A tear resisting article comprising a wall formed of laminations ofvulcanized rubber united throughout their faces, said wall having aplurality of crevices extending from one outer surface to said unitedfaces, said crevices defining closed paths, each of said paths beingseparate from the others.

5. A tear resisting sheet comprising ,a wall formed of laminations ofvulcanized rubber united throughout their faces, said wall having aplurality of crevices extending from one outer surface to said unitedfaces, said crevices defining closed curved paths, each of said pathsbeing separate from the others.

6. A tear resisting sheet comprising a wall formed of laminations ofrubber vulcanized together substantially throughout their faces, saidwall having a plurality of crevices extending from one outer surface tosaid united faces, said crevices defining closed curved paths, each ofsaid paths being separate from the others.

7. An inner tube comprising a wall formed of laminations of vulcanizedrubber united substantially throughout their faces, said wall having aplurality of crevices extending from one outer surface to said unitedfaces, said crevices defining closed paths, each of said paths beingseparate from the others.

8. An inner tube having a wall comprising inner and outer laminae ofdifierent rubber comsubstantially continuously secured to the inner faceof the outer lamina and having portions extending into said perforationsto define walls opposing the lateral walls of said perforations.

9. A tear resisting material comprising laminae of rubber composition,one of said laminae having perforations extending therethrough, theother lamina being substantially continuously secured to the face of thefirst named lamina and having portions extending into said perforationsto define walls opposing the lateral walls of said perforations.

10. A tear resisting material comprising laminae of rubber composition,one of said laminae having curved perforations extending therethrough,the other lamina being substantially continuously secured to the face ofthe first named lamina and having portions extending into saidperforations to define walls opposing I the lateral walls of saidperforations.

11. Rubber sheet material comprising laminae of different rubbercompositions substantially continuously secured together, one of saidlaminae having perforations extending therethrough, the other laminahaving portions extending into said perforations to define wallsopposing the lateral walls of said perforations.

12. An inner tube having a wall comprising laminae of rubber compositionsubstantially con-

